Low drop voltage regulator



Aug. 22, 195o K. D. JENKINS LOW DROP VOLTAGE REGULATOR Filed June 1l,1946 Patented Aug. 22, 1950 UNITED STATE-s JPATENT OFFICE (Granted underthe act of March 3, 1883, as amended April 30, 1952.8; 370 0. G. 757)The invention described herein may be manufactured and used by or forthe Government for governmental purposes without payment to me of anyroyalty thereon.

This invention pertains generally to electronic voltage regulators andmore ,particularly to a regulator which has a low voltage drop.

. In a conventional voltage regulator of the degenerative type, thevoltage drop across the series rheostat tube is usually high when theccntrol grid potential with respect to the cathode is negative. Priorefforts to reduce the high voltage drop across the series rheostat tuberesulted in gauging additional highv current carrying tubes in shuntwith the series rheostat tube. However, this proved unsatisfactorybecause it increased the size and cost of the voltage regulator. Thecurrent invention remedies this fault and produces a low voltage dropacross the series rheostat tube by operating the control grid -ofu thistube yat a positive potential with respect to its cathode. A cathodefollower stage of amplification is introduced in the degenerativefeedback circuit with the control grid-cathode resistance of the seriesrheostat tube acting as the cathode load resistor for the cathodefollower stage. It is the voltage drop across this resistance whichkeeps the control grid of the series rheostat tube l at a positivepotential with respect to its cathode.

Accordingly, an object of this invention is to provide a new andimproved voltage "regulator of greater range and that provides`regulation under greater loads or lower input voltage than previouscircuits of its type.

It is another object of this -invention to provide a voltage regulatorof the degenerative type which has a low voltage drop across the series'rheostat tube wherein the control grid is operated Fig. l is aschematic diagram that embodies the present invention; and

Fig. 2 is a schematic diagram of a speciiic adaptation thereof. f

In Fig. l oi the accompanying drawing a load circuit comprisingconductors i Vand II is energized from a direct current source I3through a 2 degenerative feedback type voltage regulator I2. The voltageregulator I2 comprises an electronic tube I4, preferably of the -highvacuum type, having an anode I6, a cathode I1 and a control member orgrid I8. The anode-cathode circuit of the electronic tube I4 isconnectedin series rela-1 non with the positive conductor lu and thedirect current source I3 by means of a positive conductor 20. Theelectronic tube Il operates as a variable impedance device to controlthe voltage impressed on the direct current load circuit includingconductors I0 and II and is referred to herein as a series rheostattube.

A second electronic discharge tube 22, having an anode 23, a cathode 2Eand a .control grid 25, is connected between conductor 20 and controlgrid I8 of the series rheostat tube I4. Itis tube 22 which is thecathode follower stage of the de generative feedback circuit and keepsgrid I8 of a positive potential with respect to cathode Il by forcinggrid I8 of the series rheostat tube I i to draw grid current. I

A suitable impedance element, such as a resistor 21, is connectedbetweenthe positive terminal of the direct current source, conductor 2li,

and the control grid 25 of the cathode follower tub:` 22. In series withresistor 21, is connected a third electronic discharge tube 30 having ananode 3i, a cathode 32 and a, control grid 33 and that serves as afeedback amplifier tube.

In order to maintain the potential oi cathode 32 of electronic dischargetube 30, substantially constant, a constant voltage device such as aglow discharge or voltage regulator tube 35, or the like, which is anelement of a voltage divider, is connected across the direct currentload circuit. A resistance 36 is placed in series with the voltageregulator tube 35 across the load circuit and their common junctionpoint is connected to cathode 32 of tube 30. The voltage regulator tube35 furnishes a substantially constant reference voltage due to itsnonlinear-current impedance characteristic.

A voltage divider comprising resistances 3l; 38 and 33 is connectedacross the direct current load circuit. Resistance 38 is provided with avariable tap lo which is connected to control grid 33 of tube 3E. Inthis manner a portion of the variation of the direct current loadcircuit voltage is impressed on the grid 33 for transmission through thefeedback circuit of the voltage regulator i2 to the series rheostat tubei4.

The operation of the embodiment of this invention shown in Fig. l of thedrawing will be ei:- plained by considering the system when it isoperating under variable load conditions. Voltage asias?? variationsintroduced from the direct current source I3 are minimized by thevoltage regulator. The voltage regulator I2 operates to control thevoltage drop across the series rheostat tube Inl so that the voltageimpressed on the load circuit remains substantially constant.

If it be assumed that the voltage of the direct current load circuitrises above the predetermined desired value, thepotential difference intube 3b between cathode 32 and control grid 33 'will increase, causingtube 30 to conduct a larger current, thereby lowering the potential ongrid 25 of cathode follower tube 22. This drop in potential willdecrease the current fiowing through cathode follower tube 22 and thegrid current drawn by grid I8. Accordingly, the series rheostat tube I4will operate to effect an increase in the voltage drop appearing acrossit and consequently lower the voltage impressed on the load circuit tothe predetermined desired value. Conversely, if the voltage across thedirect current load circuit decreases below the desired value, thepotential difference in tube 30 between cathode 32 and grid 33 willdecrease, causing tube 30 to conduct a smaller current and therebyraising the potential on grid 25 of tube 22. A consequent rise of thepotential of grid I8 in tube I4 follows and the voltage drop across theseries rheostat tube I4 decreases.

In common with previously designed voltage regulators of the samegeneral type, the apparatus in accordance with the instant invention maybe constructed entirely of miniature type tubes, with the exception ofthe series rheostat tube that will vary in size depending upon theamount of current that it is intended to conduct. Thus, it is possibleto provide a voltage regulator embodying the present invention which iscapable of being built into a very small space such as may be requiredin airborne equipment, remotely controlled equipment, or devices of asimilar nature.

In conformity with the foregoing description of a voltage regulator thatembodies the present invention it will be noted that, as an improvementover previously known voltage regulators of a comparable type, thepresent regulator is characterized by having a low voltage drop acrossits circuit and across the series rheostat tube I4 therein and hence hasrelatively small resistance.

The control grid I8 of the series rheostat tube I4 can rise above zerovoltage, or is positive with respect to the potential of its cathode andcan be drawn beyond the voltage of its cathode for increased conductanceand circuit range. The control grid I8 of the tube I4 can be drawnalmost to the voltage of the direct current source I3 of potential withwhich the voltage regulator is supplied.

A specific illustrative adaptation of the present invention is shown inFig. 2 of the accompanying drawing. Electrical components in Fig. 2 thatcorrespond to and function as components in Fig. 1 are indicated by thesame numerals primed. The designated types of tubes-and values ofcomponents are exemplary throughout. The circuit shown in Fig. 2 is`applicable for use with an S- band razon control receiver and the like.

In the circuit shown in Fig. 2 the series rheostat tube I4' is a 6V6beam power amplifier with its number 2 grid 50 connected to its plateI6. The tube 22 is a 6AK6 tube and has its number 2 and 3 grids 5I and52 respectively, connected to its plates 23". The tube 30 is a 6AK5 tubeand its number 2 grid 53 is connected in series with'a 5 kilohm resistor54 to the positive load circuit conductor it'. A secondary load circuitconductor il" is connected at the junction of the grid 53 and resistor5d. The voltage regulator tube 35 is a 991 tube. A resistor 55 is inseries with a resistor 3Q' to give 100% correction for changes ofvoltage of direct .cun'ent source i3'. The resistors 2l and 36' are eachof 470 kilohms. The remaining resistor values are: resistor 5d of 5kilohms; resistor 55 of 500 kilohms; resistor'd' of 10 kilohms; resistor3l' of 220 kiloluns; and resistor 38 of 50 kilohms. Resistors 55 and 3Q'are such that the ratio of resistor 55 divided by v39' is equal to theamplification of tube 3G. The

schematic circuit shown in Fig. 2 with the representative designatedvalues of the components therein is a successfully operative circuit anda practical adaptation of the present invention. It operates insubstantially the same manner as the described operation of the circuitthat is shown in Fig. 1.

It is to be understood that the circuits and the electrical componentassociations that are shown and described herein are submitted for thepurposes of illustrating and explaining satisfactorily operatingembodiments of the present invention and that similarly functioningchanges and modications may be made therein and particularlyarrangements that will permit a wide range of potential upon the grid I8of the series rheostat tube I4, without ,departing from the spirit and'scope of the prese/nt invention.

1. In combination, a. direct current supply circuit, a load circuit of avoltage substantially that of the direct current supply circuit, adegenerative feedback type of voltage regulator connected between saidcircuits for regulating the voltage of said load circuit and comprisinga non'linear low impedance iirst tube connected in series between thesupply circuit and the load circuit of substantially equal voltage andcomprising a plate, a cathode and a control grid, a cathode 'followersecond tube comprising a plate connected to the plate of said impedancefirst tube, a second tube cathode connected to the grid of saidimpedance rst tube and a second tube control grid, the current pathincluding the plate and cathode of the cathode follower being entirelythrough the grid cathode of the rst tube, a first resistor interposedbetween the grid nt' said cathode follower second tube and the platethereof, an electronic discharge third tube comprising a plate connectedto the grid of said cathode follower second tube, a control grid and acathode, a second resistor interposed between the cathode of saidimpedance first tube and the cathode of said electronic discharge thirdtube,'

2. In an electronic voltage regulator circuit of the degenerativefeedback type having a low voltage drop thereacross, the combination ofa direct current circuit supplying voltage to the voltage regulator, aload circuit to which the output from the voltage regulator is applied,and A the voltage regulator, the voltage regulator comprising a lowimpedance series rheostat electronic first tube having a plate, acathode and a control grid of positive potential with respect to 5 thecathode, said series rheostat rst tube being connected in series betweensaid circuits for introducing a variable low impedance therebetween andfor controlling the voltage of said load circuit such as to besubstantially as high as the voltage supplied to the regulator, acathode follower stage second tube connected in parallel across theplate and control grid of said series rheostat first tube and having acontrol grid, the current path including the plate and cathode of thecathode follower stage second tube being entirely through the gridcathode of the iirst tube,

a rst resistor connected between the plate and the grid of said cathodefollower stage second tube, an electronic discharge third tube having aplate connected to the grid of said cathode follower stage second tube,a control grid and a cathode, a voltage regulator fourth tube in serieswith said electronic discharge third tube and said rst resistor acrossthe voltage supplying circuit, a second resistor in series with the saidvoltage regulator fourth tube and the series rheostat tube across thevoltage supply circuit, a Voltage divider connected across the loadcircuit, and means adjustably connecting the control grid of saidelectronic discharge third tube with said voltage divider.

3. An electronic voltage regulator having a low voltage drop andinterposed between a direct coment supply and a load circuit, comprisinga rheostat rst tube connected in series between the high side of thecurrent supply and the high side of the load circuit and having as partsthereof a plate and a grid and a cathode, a cathode follower second tubehaving a grid and having a plate connected to the plate of the seriesrheostat rst tube and having a cathode connected with the seriesrheostat rst tube grid and maintaining the potential of the rheostattube grid above that 0I the rheostat tube cathode ksuch that therheostat tube has a low impedance, the current rpath including the plateand cathode of the cathode follower tube being entirely through the gridcathode of the ilrst tube, a rst resistor connected between the grid andplate of the cathode follower second tube, a vfeedback amplifier thirdtube having a plate connected to the cathode follower tube grid andhaving a cathode and a grid, a second resistor connecting the cathodesof the rheostat tube and the feedback ampliier third tube, a voltageAregulator fourth tube connected between the feedback amplier tubecathode and the low side of the direct current supply and with thesecond resistor in series with the series rheostat tube connected inparallel with the irst resistor and the feedback amplifier tube acrossthe direct current source, a Voltage divider across the load circuit andof a potential substantially equal to that of the direct current suppl?,and a tap connected to the feedback amplifier tube grid and Variablyengaging said voltage divider.

4. The electronic voltage regulator defined in claim 3 wherein a thirdresistor is connected between the cathode follower tube plate and thevoltage divider across the load circuit at a point negative to saidtulp.

KENNETH D. JENKINS.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 2,120,884 Brown June 14, 19382,206,123 Rinia et al. July 2, 1940 2,219,195 Norgaard Oct. 22, 1 9402,247,082 Gardener June 24, 1941 .fz-rrr- Jan

